1. Field of the Invention
The present invention concerns a vehicle adapted to travel on the surface of a planet such as Mars or the Moon in a manner that is at least partly autonomous. A vehicle of this kind, operating as a robot in the true sense, is able to move around, to circumvent obstacles and to carry out scientific, exploration and other tasks on the surface of the planet in question, for example. It is able to operate over a long period by accumulating solar energy.
To be more precise the invention is directed to providing a method of protecting a vehicle of this kind when the exterior environment in which it operates becomes hostile, leading to the possibility of irreversible material damage to some parts of the vehicle. On the Moon, for example, the duration of the night is about 14 days, during which the temperature falls to particularly low values causing failure of the electronic circuits and the battery of the vehicle, for example, making the vehicle totally inoperative, this often constituting total loss of the vehicle since it cannot be recovered and repaired. To give another example, there are frequent sand storms on Mars which could obliterate the vehicle.
A vehicle of this kind intended for a lunar mission is of very high cost and it is prudent to protect it during each period in which the exterior environment is hostile and compromises its survival, so that the vehicle can continue its current mission after any such period.
2. Description of the Prior Art
The prior art provides two solutions to the problem of protecting a vehicle during the lunar night. The first of these prior art solutions consists in a plurality of heater elements powered by the battery of the vehicle and disposed near the most vulnerable devices and circuits. The heater elements are energized as soon as the lunar night begins. To provide good protection of the sensitive equipment without requiring a considerable amount of energy it is necessary to provide it with effective thermal protection, in other words to insulate it from the exterior environment using highly insulative materials. This solution conflicts with another objective in the construction of any such vehicle, namely optimal evacuation of heat from the electric circuit during operation of the vehicle. In practise it is undesirable to use these insulative materials. However and if the insulative materials are not then this first solution requires the use of batteries occupying a very large volume, which is also incompatible with the nature of the vehicle intended to transport them.
The second solution uses a radio-isotope heat generator typically consisting of a mass of plutonium that disintegrates in a nuclear reaction to generate heat energy. Apart from its drawbacks of very high cost and difficulty of implementation, this solution has to be rejected because of its nuclear pollutant nature.
The invention is therefore directed to overcoming the drawbacks of the prior art by providing a viable method of protecting a planetary rover vehicle against an exterior environment that has become hostile.